1. Field of the Invention
The present invention relates generally to truck and/or trailer mounted portable devices for dispensing pavement repair materials and, specifically, to such a portable device for dispensing repair materials for asphalt pavements.
2. Description of the Prior Art
In the past, as many as three vehicles were sometimes needed to repair openings and potholes in asphalt, concrete and other roadway surfaces. One vehicle provided an air compressor for use with various pneumatic repair tools which were used to dress the hole, crack or cavity to be filled. Another vehicle contained liquid asphalt tack material which would be sprayed into the dressed cavity, and a third vehicle would deliver asphalt mix material to the cavity. The asphalt would then be packed, compacted and leveled by hand to complete the repair.
U.S. Pat. No. 4,196,827, issued Apr. 8, 1980, entitled "Portable Machine For Transporting Heated Asphalt Products For Use In Repair Asphalt Pavement" shows a portable machine which was designed to incorporate all phases of the pavement repair into one mobile unit. The machine has a hopper for transporting asphalt mix, and a reservoir below the hopper having a heat source. The reservoir contained liquid asphalt tack material. The heat source is used to heat the liquid tack material, and the tack material is used to heat the asphalt mix in the hopper by heat transfer. Asphalt tack material is also dispensed from the tack material tank by means of spray equipment connected to a discharge valve on the rear of the truck.
In spite of being less expensive to operate in terms of material and labor, the previously described device possessed several different disadvantages. For example, the liquid asphalt tank carried on the unit was suitable for road oils and cutbacks but was not well suited for use with asphaltic cements. Also, in the case of the device described in the '827 patent, the liquid asphalt tank was not suited for use with asphalt emulsions, because the volatile contents of the emulsions would be driven off and dry out the materials.
U.S. Pat. No. 4,944,632, issued Jul. 31, 1990, and assigned to the assignee of the present invention showed a portable unit with a separate tack oil tank which was provided with its own heat source and which was designed to prevent phase separation of the tack oil materials to overcome some of the deficiencies of the prior art devices. This tank could be used successfully with both emulsions and asphalt cutback oils.
Both of the prior art devices utilized a liquid heat transfer medium to heat the asphalt hopper of the device and maintain the asphalt mix materials therein in a workable state. While a liquid heat transfer medium has been used successfully for many years to heat the asphalt hopper, there are disadvantages associated with the use of a liquid medium. Many of these disadvantages relate to the release of volatile components of the medium as it is repeatedly heated during use. The liquid medium must also be maintained and/or replaced at regular maintenance intervals.
Accordingly, it is an object of the present invention to replace the liquid heat transfer medium used in the prior art to heat the hopper compartment of an asphalt repair apparatus with a dry, radiant heat source which does not require refill and which does not emit volatile organic emissions to the atmosphere.
Another object of the invention is to provide such a dry, radiant heat source for an asphalt repair apparatus which heat source safely and effectively heats the asphalt repair materials without hardening, burning or charring such materials.
Another object of the invention is to provide such an apparatus which is simple in design and economical to manufacture.